From the information iv been able to gather from reading articles from linguists, observers, including my own observations and research.

Appalachian English & Southern American English largely originates from the English spoken in SouthWestern England (WestCountry), Southern England, Scots-Irish or Ulster, Ireland, and The Scottish-British border, or SouthWest lowland Scotland. There also seems to be a minor London English influence and or perhaps an older version of London English that may have came to the Southern states of the United States and influenced some pronunciations as well as some words and vocabularies. There also seems to be a small minor African influence in some aspects, as well as East Anglian or East England, and French influence. However, we are mostly gonna focus on the main origins of South Appalachian & Southern American English which would be the Scots-Irish & SouthWest England English.